The microstructure and nanomechanical properties of chlamys farreri shell

The microstructure of chlamys farreri shell was observed by SEM, the results showed that the chlamys farreri shell is a kind of biological ceramic composite, which is composed of calcite, aragonite and collagen. The calcite layer has irregular laminated structure, and the aragonite layer has regular laminated structure which are composed of staight aragonite strips. The chlamys farreri shell was researched by nanoindentation test, it was shown that both hardness and elastic modulus of aragonite layer are larger than those of calcite layer. It was illustrated that the carrying capacity of aragonite layer is higher than that of calcite layer under same conditions. According to the further observation of nanoindentation apperance of chlamys faerreri shell, the crack propagation modes of two materials are different when they are loaded by external force. The crack shape of calcite is irregular, and the cracks extend along with direction of crystal boundaries, and the capacities of anti-failure and deformation are poor; but the crack of aragonite layer is relative straight, and the amount is less, so the capacities of anti-failure and deformation is preferable. The aragonite layer has excellent mechanical properties.